Interposer Patch Warpage Reduction via Underfill Curing
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Solution Overview
Problem
Existing patch on interposer structures experience significant warpage during die attach processes due to thermal expansion differences and dynamic stress, leading to reduced yield and assembly challenges in microelectronic packaging.
Innovation Solution
The method involves attaching a patch structure to an interposer using thermal compression bonding, followed by underfill curing to increase structural stiffness, thereby minimizing warpage by integrating mid-level interconnects at low temperatures and exposing the patch to high temperatures only after underfill curing, which aligns thermal expansion coefficients and reduces dynamic stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal compression bonding is used to attach patch to interposer, then assembly temperature can be controlled, but warpage still occurs due to thermal expansion differences
Solution Approach 1:
The interposer is pre-heated to a temperature close to the thermal expansion match point before patch attachment. This preliminary temperature adjustment ensures that thermal expansion coefficients of the interposer and patch are matched during bonding, preventing warpage while maintaining controlled assembly temperature
Solution Approach 2:
The temperature parameter is dynamically adjusted during the assembly process. The interposer temperature is raised to a specific range (e.g., 80-150°C) where thermal expansion matching occurs, then maintained during patch attachment to minimize warpage
2Strength
If die attach is performed at high temperature, then bonding strength is improved, but warpage increases due to thermal expansion mismatch
Solution Approach 1:
The temperature parameter is optimized to a specific range that simultaneously achieves adequate bonding strength and thermal expansion matching. By controlling temperature within 80-150°C during die attach, the method ensures sufficient bonding while minimizing warpage from thermal mismatch
Solution Approach 2:
Different temperature zones are implemented: the interposer is heated to thermal expansion match temperature, while the patch and die are heated to bonding temperature. This localized temperature control allows both thermal expansion matching and strong bonding to occur simultaneously
3Volume of moving object
If patch structure is made thinner to reduce size, then packaging density is improved, but structural stiffness decreases leading to increased warpage
Solution Approach 1:
The temperature parameter is used to compensate for reduced structural stiffness. By heating the interposer to thermal expansion match temperature during assembly, thin patch structures can be bonded without experiencing excessive warpage, enabling miniaturization while maintaining stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces warpage and improves assembly flow by stabilizing the structure, enhancing the integration of patch on interposer and die attach processes, and allows for more robust packaging with reduced thermal expansion mismatches.
Implementation Method 1
attaching a patch structure to an interposer by thermal compression bonding
Implementation Method 2
forming an underfill around an array of interconnect structures disposed on a top surface of the interposer, curing the underfill
Implementation Method 3
aligns thermal expansion coefficients and reduces dynamic stress
Data Source
AI summary
Methods of forming microelectronic structures are described. Embodiments of those methods include attaching a patch structure to an interposer by thermal compression bonding, forming an underfill around an array of interconnect structures disposed on a top surface of the interposer, curing the underfill, and then attaching a die to the patch structure.